1. Field of the Invention
The present invention relates, in general, to sunshade apparatuses for automobiles and, more particularly, to a sunshade apparatus for automobiles, which is installed in an automobile at a location near a rear window and extends a sunshade screen from a winding roll using a motor, thus shading the interior of the automobile from sunlight.
2. Description of the Related Art
A motorized sunshade apparatus for automobiles is typically installed on a rear shelf, which is located between a rear seat and a rear window inside the passenger compartment of an automobile and has low structural strength. Due to the low structural strength of the rear shelf, the motorized sunshade apparatus must have characteristics in that it does not generate shocks or vibration at the time of starting or stopping operation, has light weight, and generates little operational noise, in addition to the requirement of high operational reliability.
U.S. Pat. No. 6,216,762 discloses a sun-shade device, in which a rotary plate is installed to be rotated clockwise and counterclockwise by a motor, and first and second linking rods are jointed at first ends thereof to the rotary plate at opposite locations angularly spaced apart from each other at an angle of 180 degree and actuate left and right arm units, respectively. In operation, the sun-shade device converts rotating motion of the rotary plate into rectilinear motions of the first and second linking rods, so that, at the time of starting and stopping the operation of the sun-shade device, the motions of the elements are delayed, and thus the operation of the sun-shade device may not be stable.
Further, in the sun-shade device, a stopping means, which prevents excessive rotation of upper and lower arm members of each arm unit and comprises a pin protrusion provided on the lower arm member and an engaging groove provided on the upper arm member, is provided. However, to provide the stopping means in the sun-shade device, it is necessary to produce a pin protrusion and fit the pin protrusion into a hole, which is formed in the lower arm member, or weld the pin protrusion to the lower arm member, thus complicating the process of producing the lower arm member having the pin protrusion. Further, it is necessary to form a precise engaging groove in the upper arm member at a location corresponding to the pin protrusion. Therefore, it is difficult to form reliable stopping means in the sun-shade device. Further, the pin protrusion and the engaging groove may be deformed and abraded partially after the stopping means is repeatedly used for a lengthy period of time. In the above state, the stopping means may generate operational noise, which irritates passengers, and may not realize desired operational precision.
The sun-shade device further includes biasing means, which is provided in a shade bar to elastically bias respective upper arm members of the left and right arm units and promote the rotating motion of the upper arm members relative to the shade bar, thus realizing easy stretching of the upper and lower arm members. The biasing means provided in the sun-shade device comprises a tension spring, both ends of which extend over the upper ends of respective upper arm members and are locked thereto, so that the tension spring is elongated and thus exceeds the length of the shade bar. Thus, it is difficult to assemble the tension spring in the sun-shade device.
Further, the tension spring, which is elongated to thus exceed the length of the shade bar, generates a metal scratching noise and vibration during the extension and contraction thereof. Thus, to reduce the noise and vibration, the tension spring must be covered with a covering, such as tape or a nonwoven fabric having sound and vibration absorption properties.
Further, the tension spring, which is elongated to exceed the length of the shade bar, increases the weight of the shade bar, thereby compromising the lightness of the sun-shade device. Because the tension spring increases the weight of the shade bar, it is necessary to use increased power to move the shade bar upwards or downwards, so that a drive unit capable of generating increased output power must be used.